Biomedical subjects
Publications and source records attributed to W C Chang.
A main product (PI) transformed from arachidonic acid in carrageenin-induced granuloma in rats was structurally analysed. PI was converted to a more polar substance by the reduction with sodium borohydride. On the basis of the data on gas chromatography-mass spectrometry, its structure was identified with the hemiacetal derivative of 8-(1-hydroxy-3-oxopropyl)-9,12-heptadecadienoic acid (Thromboxane B2).
The effect of PGF2alpha on the synthesis of hexosamine-containing substances (acidic glycosaminoglycans and glycoproteins) was studied in cultured fibroblasts derived from a rat carrageenin granuloma. Treatment with PGF2alpha ranging from 0.01 mug/ml to 20 mug/ml resulted in a significant increase of the production of these macromolecules by the cells. The stimulatory effect was found significant even at the low concentration of 10 ng/ml, and could be seen as early as 3h after exposure to PGF2alpha. The hexosamine-containing substances increased by PGF2alpha revealed that 80% of the increase was due to acidic glycosaminoglycans and the rest was due to glycoproteins.
Explore the source record for details and available documents.
Early effects of various prostaglandins on the production of hexosamine-containing substances by cultrued fibroblasts, which were derived from a rat carrageenin granuloma, were studied. At hte stationary phase, the cells were exposed for 6 h to one of the prostaglandin A1 (PGA1), A2, B1, B2, D2, F1 alpha, E1, E2 or arachidonic acid in various concentrations ranging from 0.01 to 10 microng/ml for all the stimuli and from 10 pg to 10 microng/ml for PGF2alpha. The activity of the cells in incorporating 3H-glucosamine into hexosamine-containing substances (acidic glycosaminoglycans and glycoproteins) during this period was compared with that of control cells. All the stimuli tested showed more or less stimulative effect on the synthesis of hexosamine-containing substances at their specific concentrations. PGF2alpha was found to be the most potent stimulant and its stimulative effect was found significant even at the low concentration of 100 pg/ml. PGD2, F1alpha and E2 were the next potent stimuli. Their optimum dose were aroung 1 microng/ml but they still had significant stimulation at the concentration of 0.01 microng/ml. Effect of PGE2 was rather mild. Stimulation by PGA1, A2, B1 and B2 or arachidonic acid was seen at high dose, and it seemed to be non-specific. The results suggested that these prostaglandins such as PGF2alpha, D2, F1alpha and E2 play some important role on regulating the production of intercellular ground substances.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The prostaglandin synthesizing system in bovine seminal vesicles was characterized by a radiometric assay. Two main products were formed from [1-14C]-arachidonic acid, and their structures were confirmed by mass spectrometry. The less polar product was identical with prostaglandin E2 and the more polar one was identical with a new prostaglandin, i.e., 6-ketoprostaglandin F1alpha.
Differences in the mode of vascular permeability change induced by some stimulants such as chemical mediators between the early phase and the late phase of the carrageenin-induced granulomatous inflammation were investigated with the aid of 131I-human serum albumin as an indicator for the measurement of vascular permeability. In the early pregranulomatous phase of the inflammation, histamine injection into the inflammation locus markedly elevated local vascular permeability, while prostaglandins E1 and E2 showed no effect. On the other hand, in the late phase of the inflammation, where permanent granuloma tissue had been formed, prostaglandins E1 and E2 significantly enhanced the local vascular permeability, while histamine was inert.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The effects of fractionated oxidized low density lipoproteins (oxidized LDL) on the growth of vascular smooth muscle cells (VSMC) and their relationship to the formation of lysophosphatidylcholine (lyso-PC) as well as the activation of protein kinase C (PKC) were studied. VSMC were isolated from porcine aorta by explant culture. LDL was isolated from porcine blood by sequential ultracentrifugation and oxidized LDL was obtained by incubating LDL with 5 microM CuSO(4) at 37 degrees C for various lengths of time. Our results showed that LDL oxidized for 12 h and eluted from fast protein liquid chromatography at 43 min inhibited the growth of VSMC, and that LDL oxidized for longer than 48 h and eluted at 48 min stimulated the growth of VSMC. The formation of lyso-PC in the oxidized LDL correlated well with its stimulatory effect, suggesting that lyso-PC is responsible for the mitogenic effect of oxidized LDL. This stimulatory effect of oxidized LDL was inhibited by staurosporine, a PKC inhibitor. Treatment with oxidized LDL increased the activity of membrane PKC, but it decreased that of cytosolic PKC, suggesting the translocation of PKC from cytosol to the membrane in the presence of oxidized LDL. These results suggested that the oxidized LDL-stimulated VSMC growth was mediated by the formation of lyso-PC and the activation of PKC.
Mitogen-activated protein kinase (MAPK) cascade classically is thought to be involved in cellular transformation, including proliferation and differentiation. Recent behavioral studies suggest that MAPK may also have a role in learning and memory. Long-term potentiation (LTP), a candidate mechanism for learning and memory, has at least two distinct temporal phases: an early phase (E-LTP) which lasts for 1-2 h and a late phase (L-LTP) which can persist >/=3 h. Here, we report that PD 098059, a selective inhibitor of MAPK cascade, attenuates L-LTP induced by bath application of forskolin without affecting basal synaptic transmission. This effect was mimicked by direct injection of animals with MAPK antisense oligonucleotide into the hippocampal CA1 region. MAPK activity measured by using a synthetic peptide corresponding to the sequence surrounding the major site of phosphorylation of the myelin-basic protein by MAPK was enhanced by forskolin. The same antisense treatment also completely inhibited the increased MAPK activity. These results demonstrate an involvement of MAPK in the induction of L-LTP in the hippocampal CA1 neurons.
To determine whether aortic smooth muscle cells possess estradiol receptors or not, an estradiol binding study has been performed in cultured rat aortic smooth muscle cells by using an intact-cell assay. Specific binding for estradiol is shown by the cells, and the binding reaches a plateau after 15 min of incubation at 37 degrees C. The binding curve shows a saturable binding process. Scatchard analysis reveals a single population for estradiol binding with a dissociation constant of 5.0 X 10(-8) M and specific binding sites of 64 fmole per 10(6) cells (38,500 sites per cell). Molecular specificity shows highly specific binding with estradiol. Among various steroids tested, only testosterone at 10(-5) M competes slightly (9.3%) with the estradiol-specific binding. These data indicate the existence of specific, high-affinity and limited-capacity binding sites for estradiol in rat aortic smooth muscle cells. This accords with the concept that estrogen responsiveness in aortic smooth muscle cells is mediated through the estrogen-receptor binding in the cells.
Arylamine N-acetyltransferase (NAT) activities with p-aminobenzoic acid and 2-aminofluorene were determined in Helicobacter pylori, a gram-negative rod bacteria collected from peptic ulcer patients. The NAT activity was determined using a acetyl CoA recycling assay and HPLC. Cytosols or suspensions of H. pylori with and without selected concentrations of emodin co-treatment showed different percentages of 2-aminofluorene and p-aminobenzoic acid acetylation. The data indicate that there were decreased NAT activity associated with increased emodin in H. pylori cytosols. As 400 microns of emodin can obviously inhibit NAT activity both in vitro and in vivo (inhibition rate 90% and 93% for 2-aminofluorene and p-aminobenzoic acid in vitro, and 90% and 92%, respectively, for both substrate in vivo). For in vitro examination, the apparent values of Km and Vmax were 3.12 +/- 0.38 mM and 15.20 +/- 3.16 nmol/min/mg protein for 2-aminofluorene, and 0.56 +/- 0.12 mM and 0.74 +/- 0.09 nmol/min mg protein for p-aminobenzoic acid. However, when emodin was added to the reaction mixtures, the values of apparent Km and Vmax were 2.40 +/- 0.32 mM and 10.62 +/- 0.04 nmol/min/mg protein for 2-aminofluorene, and 0.23 +/- 0.02 mM and 0.62 +/- 0.08 nmol/min/mg protein for p-aminobenzoic acid. For in vivo examination, the apparent Km and Vmax were 0.82 +/- 0.18 mM and 0.92 +/- 0.21 nmol/min/10 x 10(10) colony forming units (CFU) for 2-aminofluorene, and 0.78 +/- 0.14 mM and 0.52 +/- 0.06 nmol/min/ 10 x 10(10) (CFU) for p-aminobenzoic acid. However, when emodin was added to the reaction mixtures, the values of apparent Km and Vmax were 0.50 +/- 0.08 mM and 0.62 +/- 0.22 nmol/min/ 10 x 10(10) (CFU) for 2-aminofluorene, and 0.52 +/- 0.21 mM and 0.26 +/- 0.04 nmol/min/ 10 x 10(10) (CFU) for p-aminobenzoic acid. This report is the first finding of emodin inhibition of arylamine N-acetyltransferase activity in a strain of H. pylori.
Enantioselectivity of esterases, contained in 9,000g supernatant fraction (S9) prepared from homogenate of small intestinal mucosa of male Sprague-Dawley rats and the subsequent 105,000g supernatant (cytosol) and pellet (microsomes) prepared from S9, was studied using racemic oxazepam 3-acetate (rac-OXA) as the substrate. Esterases in S9 were enantioselective in hydrolyzing either S-OXA or R-OXA, depending on a particular subcellular preparation. Cytosolic and microsomal esterases had opposite enantioselectivity and selectively hydrolyzed S-OXA and R-OXA, respectively. Enantioselectivity of esterases solubilized from microsomes with Triton X-100 (0.1%, w/v) was identical to that of the membrane-bound microsomal esterases. Cytosolic esterases were more sensitive to temperature than either solubilized or membrane-bound microsomal esterases. In the presence of paraoxon (1 microM), the esterases selective toward R-OXA in both microsomes and S9 were completely inhibited, whereas the esterases selective toward S-OXA in cytosol were inhibited by approximately 6%. These results indicate that cytosolic and microsomal esterases in rat small intestinal mucosa are distinctly different enzymes, with opposite enantioselectivity in the hydrolysis of rac-OXA.